Hi Alan, I use one HUB power control application (https://github.com/mvp/uhubctl) to investigate power switchable HUB, and find the kernel turns port power on again at drivers/usb/core/hub.c, after port power is turned off by user space. 5122 if (hub_is_port_power_switchable(hub) 5123 && !port_is_power_on(hub, portstatus) 5124 && !port_dev->port_owner) 5125 set_port_feature(hdev, port1, USB_PORT_FEAT_POWER); The main sequence for testing turn port power off like below: - uhubctl sends command to turn specifc port (eg, 2-1.4) power off. - devio at kernel gets that command, and send to hub. - port power is off, the hub_event is triggered due to port status is changed. - usb_disconnect is called, but port power is on again by kernel at function hub_port_connect. I can't find the code history why the port power needs to turn on after device is disconnected, do you know why? Any sugguestions to fix it? Thanks. Best regards, Peter Chen
